Export additional build info for use when serving builds

Over the past few month, linaro infrastructure added options for restricted hosting of build artifacts coming out of linaro infrastructure build services.

Those features namely were: EULA-restriction as well as OPENID protection of builds.

The EULA restriction was implemented using a EULA.txt trigger that allows the builds to protect its build by asking for a EULA.
It was implemented by following BPs:
 + https://blueprints.launchpad.net/linaro-license-protection/+spec/eula-handling-improvements
 + https://blueprints.launchpad.net/linaro-license-protection/+spec/multiple-eula-handling-improvements

Follow up thoughts revealed that protected publishing comes with a wider set of requirements:

 1. the eula text should be defined in the file itself
 2. the theme for displaying the EULA should be selectable
 3. the mechanism should be extensible to later add more EULA options, such as collecting user email and name information before admitting a download
 4. openid protection shoud be configurable without IS interaction

To address these, this blueprint proposes introduction of a general BUILD-INFO.txt format. The format should be extensible and should come with clear format spec version that allows to change the format in case new requirements arrive.

As such, this blueprint will close out by delivering a BUILD-INFO.txt file format that allow to select our existing EULA protection, include the EULA text and allows to configure a theme. BUILD-INFO will also be used to "configure artifacts" as "openly downloadable"

Follow up blueprints will extend the format by adding support for including hosting theme for delivering member branding, as well as include the eula text and version in the BUILD-INFO.txt. Also, there are planned follow up efforts for "openid" and "contact data collection upon EULA acceptance". Those blueprints can be found here:
  + EULA text, version and branding: https://blueprints.launchpad.net/linaro-license-protection/+spec/eula-text-version-and-branding-handling
  + OpenID support: https://blueprints.launchpad.net/linaro-license-protection/+spec/license-protection-openid-support
  + Contact data collection: https://blueprints.launchpad.net/linaro-license-protection/+spec/contact-data-collection-for-eula-publishing

Further, this blueprints will track and ensure that the existing build and platform artifacts taht currently shiip a EULA.txt and OPEN-EULA.txt have been transitioned to the new format.

BUILD-INFO.txt format:

Format-Version: 0.1
  Version of the BUILD-INFO format.
Files-Pattern: *.img, *.tar.bz2
  Filename patterns are specified using a simplified shell glob syntax. Will be used to identify protected files.
Build-Name: landing-snowball
  Would be a unique over all the builds of the same type. For now used as a placeholder and will be ignored. To be added later by build services?
Theme: stericsson
  Theme name for selecting proper theming on download and license pages, vendor name.
License-Type: open/protected
 open - Open builds. No license page is displayed.
 protected - EULA protected builds. If 'OpenID-Launchpad-Teams' is defined then OpenID protection is used, otherwise simple Accept/Decline license page is displayed before accessing protected files.
OpenID-Launchpad-Teams: linaro
  LP team names members of are allowed to access protected files. No OpenID protection if absent.
Collect-User-Data: yes/no
  Default to 'no' if not present. If the field is set to 'yes' then Name and E-Mail (some other fields?) fields are asked to be filled. If it will be needed in the future it could be expanded with 'Collect-User-Data-Fields' field later or any other approach.
License-Text: EULA full text included in BUILD-INFO.txt

- If line begins with space character ' ' it is treated as a part of last found variable which turns as multiline variable and is appended to it.
- Variable names are case insensitive.